Fan diffuser having an airfoil lattice deflector



M. B. CURLEY Jan. 20, 1953 FAN DIFFUSER HAVING AN AIRFOIL LATTICEDEFLECTOR Filed Sept. 20, 1949 MW gm fNVE/YTQ/QJ Mo ToN B.CURI EY,

HTT'Y J ZOEIUMW mmOmU LO M MN ZQFUMW LO (Mmti Patented Jan. 20, 1953 FANDIFFUSER HAVING AN AIRFOIL LATTICE DEFLECTOR Morton B. Curley,Worthington, Ohio, assignor to The Jeffrey Manufacturing Company, aC01".

poration of Ohio Application September 20, 1949, Serial No. 116,705

2 Claims. (01. 230120) This invention relates to a fan and moreparticularly to a fan having a diffuser which is constructed to diffusethe output air from the fan by using airfoil lattice deflectors and inwhich a transverse dimension of the diffuser is substantially constant.

An object of the invention therefore is to produce a fan and associateddiffuser having the above mentioned characteristics.

A further object of the invention is to provide a diffuser in which thecross-sectional area is increased as. the air passes from one sectionthereof to another through a lattice deflector and in which onedimension of the diffuser, such as its width, may be substantiallyconstant.

Other objects of the invention will appear hereinafter, the novelfeatures and combinations being set forth in the appended claims.

In the accompanying drawings,

Fig. 1 is a combination sectional and elevational view in which thediffuser may be considered as rotated either ninety degrees or onehundred and eighty degrees from its actual installation position; and

Fig. 2 is a plan view of the fan and diffuser of Fig. 1.

In order to produce an efiicient fan, such as used to ventilate a mine,it is well recognized that there should be a diffuser on the air outputside of the fan, in which the cross-sectional area through which the airtravels is increased between the discharge end of the fan proper, or, inother words, adjacent the blades, and the final delivery of the aireither to atmosphere or to a conduit leading to a mine ventilatingshaft, the first in the case of an exhaust fan, the latter in the caseof a pressure fan. Generally, the ratio of this area is of the order of3-3 /2 to 1. In other words, the effective crosssectional area at theexhaust or output end of the diffuser is preferably from three to threeand one-half times the effective cross-sectional area at its input end.

Heretofore, one accepted way of producing this desired ratio-ofcross-sectional areas in a diffuser has been to provide a frusto-conicaldiffuser which expands in diameter and in crosssectional area from itsinput position, adjacent and to'the rear of the fan blades anddeflectors,

if any, to its discharge position. Such construcundesirable distanceaway from the adjoining structure and/or to require an extensive andundesirably high base or support for the fan proper.

Another objection often encountered is that these fans set alongside abuilding or a drift mine opening and it is necessary to excavate thehill or ground slope adjacent the opening to accommodate the fan. Insuch case some-- times considerable excavation is required becauseobviously if the fan is of the suction type the large discharge openingof the diffuser cannot be permitted to discharge directly into a closelyadjacent upright or upwardly extending Wall.

The diiiuser of my invention overcomes these and other objections, Whilemaintaining the desired ratio of area of diffuser input to output, inthat a pair of side Walls of the diffuser, or at least a substantialportion thereof, are parallel throughout the various sections of saiddiffuser and are not substantially greater, if any, than thecorresponding dimension of the fan proper. Furthermore, a diffuser is soconstructed that the longitudinal axes of the several sections thereofmake obtuse angles with each other, thus making it possible to providethe overall diffuser as a turning unit so as to deflect the dischargedair upwardly, laterally or downwardly, as circumstances dictate to bedesirable. For example, in one typical installation the complete fanwith diffuser may be placed closely adjacent a structure having avertical wall with the fan proper setting close to the ground. If thefan is a suction type, that is, draws air out of the ventilating mineshaft, the deflector may have its discharge opening extending upwardlyso that any hill or wall to the rear of the deflector will in no wiseinterfere with the free discharge of the air. In another typicalinstallation the fan unit might be set close to the ground and thedeflector turned either laterally or downwardly, forcing air into a mineshaft casing or to atmosphere.

Referring specifically to the accompanying drawings, a radial blade orpropeller type fan is provided, including a fan casing or housing [0having a frusto-conical converging air inlet portion H and a generallycylindrical portion l2 adjacent the rotor l3 of said fan, which rotormay, for example, follow the construction in my Patent No. 2,307,490above identified. The rotor 13 includes radially extending blades. I4and is mounted on a drive shaft 15 carried in appropriate bearings, oneof which is seen at 16, mounted on a pedestal II. The other bearing forshaft I5 is mounted in a cowling. I8 mounted in part within the casingI0. The pedestal I1 is provided with a mounting base, as is the casingl0, so that the fan unit proper, including the parts above described,may be mounted on any desired base or foundation, such as a concretebase.

The fan illustrated is of the blower type; that is, it draws inatmospheric air and forces the air ultimately to a mine shaft casing, orthe like. If desired, it may be of the exhaust type in which the inletportion M will be connected with the ventilating mine shaft, or thelike, in a well known manner. In any case, Whether the fan proper is ofthe exhaust or pressure type, it is preferably provided with a diffuserwhich in its entirety is designated by the reference character i9, whichdiffuser has the function of converting the kinetic energy of the movingair to an appreciable extent to static energy or pressure which isessential to maintain high efliciency in the overall unit.

As illustrated in the drawings, the diffuser I9 is made up of foursections, the first diffuser section being designated 29, the second 2!,the third 22 and the fourth 23. Diffuser section 29 performs twoprincipal functions. First of all, in cooperation with the tail portionof the cowling I8 it increases the effective cross-sectional area fromits input to its output. For example, the effective input area of thediffuser section 20 in one typical illustration, which will be followedthrough purely as an example of a practical construction, is 9.41 squarefeet. This means that the effective input area through which the air canflow at the left-hand side of diffuser section 2%, as viewed in Figs. 1and 2 of the drawings, is 9x11 square feet. This is the area of theopening into said section 2!), less the area of the cowling l8 at saidopening.

The output area of said section 23, which is the area adjacent theright-hand side, is 12.65 square feet. It is to be noted that the axisof the air travel through the section 29 is not changed and, asillustrated in the drawings, is substantially perpendicular to a planethrough the output area of said section 20.

The discharge area of the section 29 is, of course, equal to the inputarea of the section 2|. A characteristic of sections 2|, 22 and 23 isthat opposite elements of the side walls are parallel though generallyunequal in length, and the direction and volume of the air flow througheach section is constant for the entire section, except for the airfoillattice deflectors which may be considered for practical purposes asseparate from the sections themselves. In this connection it may well bestated at this time that there is an airfoil lattice deflector 24interposed between the sections 2| and 22, and a similar deflector 25interposed between sections 22 and 23. Reverting to a consideration ofthe parallelism between opposite side walls of each section 2|, 22 and23 Within itself, it is to be noted that as illustrated in Fig. 2 of thedrawings the two lateral sides of said section 2| are parallel andspaced apart, constituting vertical side walls. The bottom wall of thissection is a substantially horizontal flat wall designated by thereference character 28 (see Fig. 1). The top wall of this section 2| hassubstantially zero longitudinal dimension and this must not be confusedwith the upwardly sloping top wall, as viewed in Fig. 1, whichconstitutes in effect the wall of the lattice deflector 24 which, ashere illustrated, is built in as an integral part of the section 2|,though functionally it must be considered as separate therefrom.

From the above description of section 2| it is obvious that its input isrectangular in crosssection and consequently the adjacent continuingwall or end of the section 20 must likewise be rectangular. It isfurther evident from the above description that the forward or left-handend of the section 20 is round. Consequently the diffuser section 22 notonly acts as the first step in the diffusing function, but also is atransition piece connecting the round discharge opening of the fansection |2 with the rectangular input opening of the diffuser section2|.

The longitudinal axis of the section 2| coincides with the longitudinalaxis of the section 20 and thus there is no change in the direction ofthe air in moving from section 25! to section 2|. The discharge end ofthe section 2| is, of course, the same size as the input or receivingend of section 22 and they are joined along a plane which makes an acuteangle with the longitudinal axis of said section 2|. The angle of thisplane with a plane at right angles to the longitudinal axis of thesection 2| is generally designated in the art by the Greek letter ,6(beta). This angle is known in the art as the stagger angle.

As previousl mentioned, elements of opposite side walls of the section22 lie in parallel planes. The cross-sectional area of this section 22is herein to be understood as the area of a plane to which the axis ofsaid section is perpendicular and which intersects at right angles thefour right angularly related sides of said section 22 or projections orextensions thereof. In the illustrative embodiment of the invention thiscrosssectional area of section 22 is fixed at 20.5 square feet. Theabove definition of cross-sectional area also applies to sections 2| and23.

The air in passing from the section 2i to the section 22 is deflected bythe airfoil lattice deflector 24, and the direction of travel of the airin passing through the section 22 is substantially along thelongitudinal axis thereof which is designated by the arrow in saidsection. The angle between the direction of travel of said air insection 22 and its direction of travel in section 2i is designated as 0(theta) in this art and is known as the turning angle.

It may be stated that there is a recognized relation in the art betweenthe cross-sectional areas of two such adjacent sections through whichair must travel and the turning angle and the stagger angle which isexpressed by the equation:

1@ cos (B6) A cos 6 In this case the ratio of A22 to A21 is:

From this it is possible to pick out a desired relation of the turningangle to the stagger angle from standard charts for any given solidityof the lattice deflector.

The deflector section 23, as above mentioned, also has opposite sidewalls lying in parallel planes. The cross-sectional area of this sectionis increased over the cross-sectional area of section 22 and in theillustration given the ratio is 1.62 to l, the same as the ratio betweensections 22 and 2|, so that the cross-sectional area of section 23 is33.2 square feet.

To reiterate briefly, the cross-sectional area. or, in other words, thearea at right angles to all the side walls of the section 22, is 20.5square feet, which is 1.62 times the cross-sectional area of section 2|.

The cross-sectional area of section 23 is likewise 1.62 times thecross-sectional area of section 22. Therefore, each succeeding section2|, 22 and 23 has a greater cross-sectional area than the precedingsection. Furthermore, the area of each section 2 I, 22 and 23 is uniformwithin that section itself. In order for the sections 2!, 22 and 23 tobe joined together so that the output perimeter of a preceding sectionis the same as the adjoining input perimeter of a succeeding section,the longitudinal axis of each succeeding section 22 and 23 makes anobtuse angle with the axis of each preceding section. As a consequenceof this, as the air progresses from section 2| to section 22 to section23 it is inherently deflected so that the diffuser function is carriedout simultaneously with a change in direction, making it possible andpractical to turn the direction of flow of the air as it issimultaneously diffused, thus maintaining the desired efficiency of thefan.

As above pointed out, the input area of the first diffuser section 20was 9.41 square feet. The uniform cross-sectional area of the diffusersection 23 was 33.2 square feet. The ratio of the area of section 23 tothe input area of section 20 is:

33.2-:-9.41=apprx. 3.5

which is the desired ratio of expansion of the air within the diffuserconsistent with high efiiciency for the fan as previously set forth.

It may be noted that after the air leaves the airfoil lattice deflector25 it is not further expanded in the casing section 23 and it might besuggested that since there is no further expansion in this section thatit serves no useful purpose, particularly where the fan is of theexhaust type and discharges from the diffuser to atmosphere. In otherwords, it might be suggested that the air simply be discharged fromdeflector 25 to atmosphere. It has been found, however, that it is verydesirable to provide such a uniform cross-sectional area of the casingsection following the final lattice deflector.

In case the fan is of the exhaust type and it exhausts to atmospherethere is no occasion to attach any other casing section to the diffusersection 23. As illustrated, particularly in Fig. 1 of the drawings,however, the fan is shown as of the blower type and consequently thereis a casing section 21 attached to the diffuser section 23. The casingsection 27 is not intended to have any diffuser function but merely actsas a casing to deliver the properly diffused air to a mine shaftventilating conduit, housing, or the like.

From the above description it is obvious that a fan, such as a mineventilating fan, either of the exhaust or pressure type, has beenprovided, in which the difiuser is so constructed that it may be placedconveniently in positions which heretofore have produced structuralproblems, particularl in that the diffuser need not have substantiallygreater width or lateral horizontal dimension than the fan proper andthat the discharge opening of the diffuser may extend upwardly, thus notrequiring any elevating base for supporting the fan or the deflector andradially deflecting the air, if discharged to atmosphere, upwardly or ina direction that an adjacent building, hill or mountain slope, or thelike, will not interfere with the free discharge of said air. Likewisethe difiuser construction in the case of a pressure or blower fanprovides for inherent turning of the housing which directs the air intothe mine shaft conduit or housing, readily lending itself to aninstallation where such is incorporated in a mine shaft and extendingdownwardly into the ground. It has been found that there are numerousproblems created by field conditions in which the arrangement of myinvention is a very effective solution and greatly reduces the totaloverall cost of an installation without in any way sacrificing theefficiency of the fan.

In the illustration given there are four sections to the diffuser andtwo airfoil lattice deflectors which are between the last three sectionswhich effect a change of air direction. This number is found desirablein the illustration given. In som installations it is possible that onlya single lattice deflector may be required between two diffusersections. It is possible that in some installations three suchdeflectors will be required. In this regard it is to be noted that thereis an airfoil lattice deflector at each position where adjoiningsections have their longitudinal axes angularly related.

Obviously those skilled in the art may makevarious changes in thedetails and arrangement of parts without departing from the spirit andscope of the invention as defined by the claims hereto appended, andapplicant therefore wishes not to be restricted to the preciseconstruction herein disclosed.

Having thus described and shown an embodiment of the invention, what itis desired to secure by Letters Patent of the United States is:

1. A fan including a discharge diffuser having a minimum input to outputcross-sectional area ratio of about three to one, said diffuser havingat least two substantially parallel side walls throughout its length andhaving adjacent sections whose longitudinal axes make an obtuse anglewith each other, and an airfoil lattice deflector between said adjacentsections of said diffuser.

2. A radial blade type fan including a casing having a generallycylindrical portion adjacent the fan blades, a diffuser including afirst section connected to the output side of said cylindrical casingportion in the direction of air flow, said first section being generallycylindrical at its input end adjacent said cylindrical casing portionand rectangular adjacent its output end and increasing in effectivecross-sectional area from its input end to its output end, a seconddiffuser section connected to said first section and having alongitudinal axis coinciding with the longitudinal axis of said firstsection, a third section having a substantially constant cross-sectionalarea greater than the cross-sectional area of said second section andconnected with the output side of said second section, said thirdsection having a, longitudinal axis making an obtuse angle with thelongitudinal axis of said second section, and an airfoil latticedeflector between said second and third sections.

MORTON B. CURLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,080,757 Blomberg May 18, 19372,144,035 Smith Jan. 17, 1939 2,446,879 Kennedy Aug. 10, 1948

